Titan’s seas of sand

A new analysis of data from the Cassini/Huygens mission shows that areas once …

The atmosphere of Saturn's largest moon, Titan, is a thick organic haze that prevents examination of its surface in visible wavelengths. Fortunately, Cassini, the probe now orbiting Saturn, was sent equipped with radar, which it has used to map the surface features of Titan. Much to the surprise of the scientists receiving the data, it found that dark areas near the equator, once thought to potentially be hydrocarbon seas, were seas of another type: sand, complete with dunes. The results are published in the latest issue of Science, and come with a press release for those of you who can't access the articles.

Of course, Titan's chemical composition is nothing like the earth's, so we're not talking sand as we understand it. In fact, one of the scientists involved suggests that we're not talking about much as we currently understand it:

These images from a moon of Saturn look just like radar images of Namibia or Arabia. Titan's atmosphere is thicker than Earth's, its gravity is lower, its sand is certainly different -- everything is different except for the physical process that forms the dunes and resulting landscape.

The press release notes that Titan's winds aren't caused by thermal convection as on earth (the sun doesn't accomplish that much in terms of heating at Titan), but rather the intense gravitational pull of nearby Saturn, which creates tidal forces on the atmosphere that are over 400-fold as strong as the Earth's Moon can generate. The source of the sand isn't yet clear, but it's suggested that it may result from methane rain-driven erosion. Even though rain, on average, is uncommon on Titan, it could be that some rare storms are strong enough to have an impact.

Meanwhile, scientists at the University of Arizona who ran one of the imagers on the Huygens probe that landed on Titan's surface have put together a movie of the probe's plunge towards Titan. The movies and other information from the group are available at their website.